1. Field of the Invention
The present invention relates to a numerical control device, and more specifically a numerical control device having plural systems capable of high speed response for transmitting information between systems at high speed.
2. Description of the Related Art
The present invention relates to a numerical control device, and more specifically a numerical control device having plural systems capable of high speed response for transmitting information between systems at high speed.
In a numerical control device used for control of an industrial machinery and the like, a numerical control device is included which divides plural axes to be controlled to plural groups (systems) and controls each group in parallel (for example, Japanese Patent Laid-Open No. 05-324046, Japanese Patent Laid-Open No. 2004-086306, etc.) In the numerical control device, axis control period (interpolation period) of each axis is generally same, and a multiple control for controlling each axis with different interpolation period is not especially performed.
During performing of the multiple system control, when an information generated at an interpolation period of a system is tried to be read by other system, since usually order of each processing such as information generation processing and information reference processing executed in each system is not determined, it is impossible to securely read the information at the same interpolation period to be read in the next interpolation period as shown in FIG. 7.
Therefore, control which requires closer synchronization (high speed response) between systems by reading an information generated in a system by the other system can not be implemented. For example, even when, based on information of operation status of program or current position of a system, operation of program of the other system is required to be immediately started, since delay for interpolation period is generated by the above restraint, it is difficult to implement high speed response.
A specific example having the problem of the delay for an interpolation period is described below. FIG. 8 is a schematic diagram illustrating gap control in which a numerical control device is automatically moved up and down according to positioning operation in horizontal axes (X axis and Y axis). Conventionally, it is possible to make gap control axis move in synchronization with the horizontal plane axes, since the up/down motion of the gap control axis is controlled in the same system, for gap control. However, since the up/down motion of the gap control axis is automatically operated by the numerical control device at present, the machine manufacturer can not uniquely customize the operation.
For enabling the customizing of the up/down motion, gap control method by multiple system type for controlling the gap control axis by other system than a system for controlling the plane axes. Here, as an example using program operation which operates the gap control axis, a method for starting axis movement by a cycle start signal.
In the method, when the multiple system control is introduced as it is, since starting of the motion of the gap control axis is delayed by an interpolation period to the motion of the plane axes, delay between the systems may cause contact of a nozzle and a workpiece at starting of positioning when a machining head moves at high speed, or completion of positioning may be not in time for starting of the next machining causing machining defect.
To solve the problem, a method in which interpolation periods of all systems are shortened to be a high speed interpolation period when the multiple system control is introduced. However, when all systems are operated at the high speed interpolation period, a CPU is significantly burdened and a high capacity CPU is required. Thus the method is not cost effective way.